Plasma C-reactive protein concentrations in active and passive smokers: influence of antioxidant supplementation

Abstract

Objective: C-reactive protein (CRP) may directly affect the progression of atherosclerosis, and therefore, may be a target for reducing disease risk. The objective was to determine whether antioxidant supplementation reduces plasma CRP in active and passive smokers.

Design: Randomized, double-blind, placebo-controlled, parallel group trial with 2 months exposure to study supplements.

Setting: Berkeley and Oakland, California.

Subjects: Healthy adult men and women, consuming <4 daily servings of fruits and vegetables, and who were actively or passively exposed to cigarette smoke. Analysis was limited to participants with detectable baseline CRP concentrations and no evidence of inflammation associated with acute illness at baseline or follow-up as reflected in CRP elevations (> or =10.0 mg/L). A total of 1393 individuals were screened, 216 randomized, 203 completed the study, and 160 were included in the analysis.

Interventions: Participants were randomized to receive a placebo or vitamin C (515 mg/day) or antioxidant mixture (per day: 515 mg vitamin C, 371 mg alpha-tocopherol, 171 mg gamma-tocopherol, 252 mg mixed tocotrienols, and 95 mg alpha-lipoic acid).

Measures of outcome: Change in plasma CRP concentration.

Results: Vitamin C supplementation yielded a 24.0% reduction (95% confidence interval, -38.9% to -5.5%, p = 0.036 compared to control) in plasma CRP, whereas the antioxidant mixture and placebo produced a nonsignificant 4.7% reduction (-23.9% to 19.3%) and 4.3% increase (-15.1% to 28.2%), respectively. Results were adjusted for baseline body mass index and CRP concentrations.

Conclusions: Plasma CRP itself may serve as a potential target for reducing the risk of atherosclerosis, and antioxidants, including vitamin C, should be investigated further to confirm their CRP-lowering and anti-inflammatory effects.